If your brother was using a power of attorney to administer your mother's estate after she died, he was acting without any legal authority. The main documents folks use to provide for handling their estates are (1) a Will, which only becomes effective when the testator (the person who signs the Will) dies, and (2) a Power of Attorney which allows their attorney in fact to administer their estate only until they die. At that point the Will becomes the main document. If either of your parents had created a Testamentary Trust, that would be used to allocate larger assets like real estate, business interests and investment accounts. Based on your message, I would suggest that you consult with a local attorney ASAP.
Answered on Jun 22nd, 2017 at 6:55 PM